The implementation of packaged semiconductor devices with sensors, especially those which require environmental exposure such as humidity, light, gas, and pressure, currently utilize one of two known sensor integration methods. The first is custom packaging which exposes the silicon (or other integrated circuit (IC) substrate) to the environment. The second is separate circuit board-level integration of the packaged IC with a packaged sensor device.
The first method currently used implements the sensor on-chip during the wafer fabrication process by forming a capacitive sensor on the die. While this is a low-cost and fully integrated solution, special packaging is required to expose the on-chip sensor to the environment. These custom packages are significantly more expensive than traditional packages, and they expose the entire IC chip's top surface to environmental conditions. Such chip exposure can cause problems such as humidity trapping, and compliance failures.
The second method separates the analog front end (AFE) of the IC that processes the sensing signal and the packaged sensor. This method requires both of these separate components to be interfaced at the circuit board level on a printed circuit board (PCB) which is not an integrated solution, and thus raises the cost.